The present invention relates to an internal-combustion engine cylinder head comprising four valves and an injection valve arranged in the center, and more particularly, to a cylinder head comprising a closed runner arranged concentrically to an injection valve axis and connecting a compression bottom with a top side of the cylinder head, feeding bores and two additional supply bores for permitting coolant flows to the cylinder head, bores extending from the feeding bores to an interior coolant space of the cylinder head, a collecting pipe through which coolant is conveyed from the interior coolant space of the cylinder head, and two inlet ports for air and two outlet ports for exhaust gases of the internal-combustion engine.
Cylinder heads are known which, for optimizing combustion, are equipped with four valves on two inlet and two outlet ports, respectively, and with an injection valve arranged in the center in the cylinder head. In such cylinder heads, special attention must be paid to the fact that coolant is guided as closely as possible past the valve seats and the injection valves so that the heat resulting from the combustion can be carried away without any impairment of the stability of the combustion-space-side compression bottom of the cylinder head which is highly stressed by heat and ignition pressure.
For improving the stability of cylinder heads comprising four valves on two inlet and two outlet ports and an injection valve arranged in the center in the cylinder head, a closed runner is arranged in the center around the injection valve. The runner connects the compression bottom with a top side of the cylinder head so that forces onto the compression bottom can be removed in a far-reaching manner in the cylinder head. The runner is contained from the compression bottom to the top side of the cylinder head in a coolant space which is bounded by precast walls for the inlet and outlet ports. Coolant flows through bores in the compression bottom, enters the coolant space surrounding the runner while being centrally aimed at the injection valve and is discharged from the cylinder head by way of a collecting pipe.
The known approach has a disadvantage, however, in that the coolant space arranged centrally around the injection valve and the arrangement of the bores for the coolant limit the design possibilities for the inlet and outlet ports in the cylinder head. A further disadvantage is that the amount of coolant flowing around the valve seats on the inlet and outlet ports in the cylinder head is not sufficient.
It is an object of the present invention to provide a cylinder head having a high stability, good cooling characteristics and improved design possibilities for inlet and outlet ports.
This object has been achieved in accordance with the present invention by a cylinder head for internal-combustion engines in which the inlet ports are cast to the runner. Transverse bores are contained in the compression bottom. The first transverse bores intersect at an obtuse angle the first coolant bore, and second transverse bores intersecting at an obtuse angle the second coolant bore. The first transverse bores intersect at a point, and the second transverse bores intersecting at another point. A first and a second transverse bore meet at a point, and the respective other transverse bores lead through an overflow opening eccentrically between the outlet ports into the interior coolant space.
For improving the combustion, the intake ports in the cylinder head according to the present invention are provided with a profile so that the intake air is acted upon by a swirl. In order to be able to produce this profile, the inlet ports are cast to a bore arranged in the center in the cylinder head so that a separate wall, and therefore a coolant space on an inlet side of the bore, is omitted.
According to the present invention, bores for the coolant extend in the compression bottom of the cylinder head in such that inlet ports cast onto the bore for generating a swirl as well as outlet ports not cast on the bore in the proximity of valve seats are surrounded on all sides by coolant. By way of these bores, the coolant is fed to a coolant space of the cylinder head situated between the outlet ports. The bores for the coolant lead out on an eccentric overflow bore between the outlet ports into the coolant space.
According to a further feature of the present invention, additional bores for coolant are advantageously provided on the inlet ports of the cylinder head. Thereby the cylinder head is cooled uniformly on the inlet and the outlet side, and thermal stresses in the cylinder head are reduced. Another bore on the side of the inlet ports in the cylinder head simplifies the machining of the cylinder head.
In yet another advantageous aspect of the present invention, the coolant bores intersect at points which are connected by overflow bores with the interior coolant space for improving the coolant throughput through the cylinder head. For a uniform flow and for lowering the flow resistance of the bores for the coolant, the precast overflow bores are finished mechanically.